Signaling system



April 16, 1940. w` P, PLACE 2,197,417

' SIGNALING SYSTEM v Filed March 14, 1959 2 SheetsSheet 1 I gel@` ZA hmmm@ H96' uuwwwm 5 01 2 opljr'eqaency 10g/ole, On Period r f r-x @amy/m2, HIS ATTORNEY April 16, 1940. w. P. PLACE SIGNALING SYSTEM Filed March 14, 1939 2 Sheets-Shea?l 2 mvENToR Place ZUL'ZLU AHIS ATTORNEY Patented Apr. 16, 19740 UNITED STATES PATENT oFFIcE SIGNALING SYSTEM Application March 14,

Claims.

My invention relates to signal systems, and more particularly to signal systems for railways. I shall describe several `forms of apparatus embodying my invention, and shall then point out 5 the novel features thereof in claims.

A feature of my invention, is the provision in signal systems of the type here contemplated of novel and improved means ior operating a code following relay or other electro-magnetic device in step with signaling currents of different code rates, each code rate being' predetermined to reflect a given control condition. When apparatus embodying my invention is used for signal systems for railways, another feature of the invention is the provision of novel and improved train carried apparatus responsive both to the coded alternating current now in general use in cab signal systems by railways, and to alternating current of different low frequencies, such low frequencies being, for example, of the order of the code rates impressed upon the standard 100 cycle alternating current of the present day cab signal systems. Hence a train equipped with such apparatus ,can` be used with either a rst territory of a railway where the track circuits are supplied with alternating current of a given frequency such as 100 cycles per second coded at predetermined code rates or with a second territory of the railway where the track circuits are supplied with alternating currents of different frequencies which are equal to said code rates.

Still another feature of my invention is the provision of novel and improved means for signal systems of the type here involved, wherewith low voltage electron tubes may be used in the receiving apparatus, Again, when long track crcuits are used a feature of the invention is the provision of novel and improved means wherewith code distortion is eliminated and broken rail protection to a greater degree is assured. rOther features and advantages of my invention will appear as the specification progresses.

In the accompanying drawings, Fig. l is a diagrammatic view of one form of apparatus embcdying my invention when used as the train carried apparatus of a low power current impulse type of railway cab signal system. Figs. 2 and 3 are diagrammatic views of another form of apparatus embodying my invention when used `5,() for a. combined wayside and cab signal system for railways, Fig. 2 being the train carried portion oi the apparatus and Fig. 3 being the trackway portion of the apparatus, and wherein the train carried apparatus of Fig. 2 is provided with two receiving channels one responsive to alternating 1939, Serial No. 261,737 (Cl. 24E- 63) current of say, for example, 100 cycles per second coded at different code rates and the other channel responsive to alternating currents of frequencies equal to said code rates. f Fig. 4 is a diagrammatic View of a modied form of the train carried apparatus of Fig. 2, also ,embodying the it? and II,` an amplifying electron tube VTI, a

detector electron tube'VTZ, two code following relays MRI and MR2, a deionizing vunit comprising a condenser Ci and a resistor R3, a reactance unit RC, a decoding unit DU and a cab signal CS, together with e. suitable source of current. Y

The inductors l and H are mounted on the train in inductive relation with the track rails la and Ib, respectively, for inductively receiving energy in response to current impulses flowing in the rails, the track rails Ia and Ib being the rails of the track over which the train equipped with the apparatus of Figi is moving. Inductors I Si and I I are connected in accordance with usual `practice so that eiec'tromotive forces induced therein. by current flowing in the rails in opposite directions are additive.

The amplifying tube VTI is preferably of the high vacuum type adaptable of operation at' low plate voltage. The detector tube VT? is preferably of the controlled ionization type adaptable of operation at low plate or anode voltage. As here .shown both tubes VT! and V'I2 are of the indirect heater type.

lThe reference characters 32B and 32N designate the positive and negative terminals, respectively, of a suitable source of direct current such as a battery or generator not shown, the voltage of the source being of relatively low voltage such as of the order of 32 volts.

The filaments I3 and I4 of the respective tubes VTI and VTZ are serially connected in a circuit receiving current from the terminals 32B and SiN, a resistor I2 being interposed in this circuit to effect proper heating of the tubes. Inductors I9 and Il which are connected together in the manner stated hereinbefore, are connected in a grid circuit for the first stageftube VTI, by virtue of the left-hand terminal of inductor I 0 being connected with the grid I1 of tube VTI and the left-hand terminal of inductor II being connected to the negative side o .filament I3 of the tube, and by the cathode of tube VTI being connected to a mid terminal of a resistor IS connected in multiple with iilainent 3. This connection of cathode i5 provides a desired biasing potential of grid ll' with respect to the cathode I5. The plate circuit of tube VTl extends from positive terminal 32B of the current source over a resistor Rl, plate i8 of tube VTI, tube space to cathode l5, the left-hand portion of resistor l5 and then to the negative terminal 32N of the current source. The parts are preferably adjusted so that tube VT! operates on the straight line portion o the gridwoltage plate current characteristic. A

The detector tube VTi is ol the controlled ionization type having an anode it, a cathode 20 and a control grid 2l as well as the filament I4 the latter of which is heated in the manner pointed out hereinbeiore. The grid 2 of tube VTS is electrostatically coupled with the plate circuit of tube VTI through a coupling condenser C2 and a resistor R2 in the well known manner. The plate or anode circuit of tube VTl involves terminal 32B, winding 22 oi a code following relay NIRI, anode I2, tube space to cathode 2li, a mid terminal and left-hand portion oi resistor I2, resistor I6 in multiple with filament i3 of tube VTI and terminal 32N of the current source. The parts are so proportioned that the normal bias potential oi' grid 2i with respect to cathode 2l] causes the anode circuit to be ineffective to create ionization for the tube VT2, so that the tube is non-conductive and code following relay MRS is denergized and released.

A condenser Ci and a resistor are associated with tube VTZ to form a deionizing unit lor that tube. Resistor R3 is connected across condenser Ci over back contact 23 of relay MRI and condenser' Cl is connected across anode I9 and cathode 2t or tube VTZ over a front contact 24 or" relay MRI. The manner or" operating the code following relay MRI when an electrornotive force is periodically applied to the grid 2I or tube VT2, and the manner of deionizing the tube VTi.' subsequent to each such electromotive force will be pointed out when the operation of the apparatus is explained Another or second code following relay MR2 is governed over the back Contact 28 or" code following relay MTR-i, and a reactance unit RC. The unit RC preferably consists of a. winding 25 mounted on a magnetic core and is controlled over back Contact 3i of code following relay MRI. The code `following relay MR2 is provided with a rst or top winding 26 and with a second or lower winding 2l. At such time as relay MRi is released closing back Contact 28, the relay MR2 is energized and picked up by virtue of a circuit including terminal 32B, back contact 22, top winding 2S or relay MR2 and terminal 32N. The winding oi react-ance unit RC is energized over a circuit involving terminal 32B, back contact il of relay front contact 29 of relay MR2, winding 25 and terminal 32N. A portion of winding is connected across the 'lower winding 2l' or relav MR2 to cause, as will shortly appear. a delay in the picking up of relay when relay Milli is being operated.

The code following relay MR2 controls frequency decoding unit DU which may be or standard type, the input side of the decoding' unit DU being controlled over a circuit receiving current from terminals 32B and 32N and which circuit includes front contact 2t of relay MR2. Hence,

current impulses are supplied to the decoding units DU at a rate corresponding to the rate at which the code following relay MR2 is operated.

In accordance with usual practice a relay TA connected with the output side of decoding unit DU is effectively energized and picked up only when the relay MR2 is operated at a predetermined code rate which I shall assume for illustration to be 18() cycles per minute or 3 cycles per second. A relay TR connected with the cutput side of decoding unit DU is effectively energized and picked up only when code following relay MR2 is operated at a different predetermined code rate which I shall assume for illustration to be 12C cycles per minute or 2 cycles per second. Also, a relay TL connected with the output side of unit DU is effectively energized and picked up when code following relay MR2 is operated at either of the code rates of 2 or 3 cycles per second and also when relay MR2 is operated at a third predetermined code rate which latter code rate l' shall assume for illusuraticn to be '75 cycles per minute or 11/4 cycles per second.

The relays TA, TR and TL govern the operating circuits of a cab signal CS here shown as of the position light type. When relay TA is picked up closing front contact 32 a circuit for lamp 33 is closed and lamp 33 is illuminated so that signal CS displays a clear signal indication. When relay TA is released closing back contact 34 and relay TR. is picked up closing front contact 35, the two lamps 35 and 31 of signal CS are illuminated to display an approach medium indication. When both relays TA and TR are released closing the respective back contacts 34 and 38, and relay TL is picked up closing iront Contact 39, a lamp 4U of signal CS is illuminated to display an approach signal indication. Again, when all three relays TA, TR and TL are released closing respective back contacts 34, 38 and 4I, a lamp 42 of signal CS is illuminated to display a slow speed signal indication.

As stated hereinbeiore, the train carried apparatus of Fig. l is adaptable of use with a low power current impulse signal system, such as, for example, described in my copending application Serial No. 222,883, filed August 3, 1938 for Signal systems. apparatus of l is adaptable o1' cooperating with the trackway apparatus of Fig. l0 of my aforementioned copendng application Serial No. 222,883, and by which trackway apparatus the track rails Ia and Ib of a track section of a stretch of railway is supplied with impulses of direct current at the code rates of 180, 120 and 75 cycles per minute according to dil'erent traic conditions in advance of the section. A single current impulse of direct current is supplied to the track rails each code cycle, each current impulse being oi relatively high peak voltage and of short duration, the duration of the impulse being only a small portieri oi the code cycle. Reference is made to said copending application Serial No. 222,883 for a full description 0i such trackway apparatus and it is suiicient for the instant application to point out that under either clear trailic conditions or approach medium traffic conditions in advance of a track section the track rails Ia and lb of that section are supplied with current impulses of 180 code rate. When approach trame conditions exist in advance of that section the track rails are supplied with current impulses of the 120 code rate,

Specifically, the train carried lll Cil

III

and when the section immediately in advance of the section is occupied the track rails are supplied with current impulses of the 75 code rate, and when a train already occupies the track section the current impulses are shunted by the leading train.

In describing the operation oi the apparatus of Fig. 1, I shall rst assume that direct current impulses of the code rate of 180 are supplied to the track rails Ic and Ib, which is the code rate used to reflect clear tramo conditions. Each direct current impulse induces electromotive forces in inductors and ll, which electromotive forces add their effects and the resultant electromotive force is applied to the grid of the amplifying tube VTI so that the wave form of the electromotive force is reproduced on an enlarged scale in the plate circuit of tube VTI. Since each current impulse is in effect a single surge of direct current, the induced electromotive force has a single cycle Wave form, the first half cycle of which is of relatively large amplitude and the second half cycle of which is of relatively small amplitude. The connections are such that the first half cycle of the Wave form of the electromotive force as reproduced in the plate circuit of tube VTI, causes the grid 2| of tube VT2 to be more positive in potential with respect to cathode 2B with the result that tube VT2 ionizes and becomes conductive. When tube VT2 becomes conductive and current flows in its anode circuit the code following relay MRI is energized and picked up. With relay MRI picked up closing front contact 24 condenser CI is connected directly across the anode I9 and cathode 20. The anode current which has been owing through the tube VT2 is diverted and for an instant flows through condenser CI. During this instant the potential of anode I9 with respect to the cathode is reduced to substantially zero and tube VT2 deionizes and is restored to its nonconductive condition. When condenser CI has been fully charged current ceases to ow and relay MRI is deenergized and released, closing back contact 23 to connect resistor R3 across condenser CI. Condenser CI is quickly discharged through resistor R3 and made ready for the next operation of relay MRI in response to the next electromotive force caused by the next current impulse flowing in the rails Ia and Ibi. A recti fier 43 may be connected in shunt across winding 22 of relay MRI to dissipate the energy stored in the magnetic circuit of that relay when current is flowing and thereby prevent voltage surges which might otherwise tend to cause tube VT2 to again ionize when the current ow is being diverted by condenser CI. Condensers 44 and '45 may be provided and connected across the elements of tube VT2 in the manner shown `in Fig. 1 to improve the operation of the tube. It should be noted that since there is no current ow in tube VT2 until a breakdown begins, condensers 44 and 45 do not make the circuits unstable, condensers 44 and 45 being effective to insure that once conduction of tube VT2 is started it is carried on to completion. However, condensers 44 and 45 may not be needed. It should 'also be noted that the second half cycle of the wave form of the induced electromotive force as reproducedin the plate circuit of tube VTI increases the negative potential of grid 2l of tube VT2 with respect to its cathode 2U and hence tends to prevent ionization of that tube by the second half cycle of the electromotive force.

It follows that code following relay MRI is operated once 'for each current impulse supplied to the track rails Ia and Ib, the time relay MRI is picked up being, however, only a small portion of the code cycle interval of the track circuit current. In Fig. 5a this operating characteristic of code following relay MRI is illustrated, the period relay MRI is picked up during each code cycle being indicated as the on period of the relay and the period the relay is released during each code cycle being indicated as the off period for the relay.

When the current impulses supplied to the rails Ia and I b` are of either the 120 or 75 code rate, the operation of the apparatus of Fig. 1 is similar to that thus far explained in connection with the code rate of 180 except the on period of the relay MRI is a somewhat smaller portion of each code cycle because the time required to deionize tube VT2 and deenergize relay MRI is the saine under each code.

Consequently, the code following relay MRI is operated at a code rate which corresponds t0 the code rate ofr the current impulses supplied to the track rails of the section occupied by the train butwith unequal on and off periods. f`

It should be noted that because both the normal grid bias potential and anode voltage of tube VT2 are derived from the same source of current, operation of tube VT2 is immune to a reasonable amount of variationin the voltage of the current source.

Since the operation of a decoding unit of the standard forms in present day use is most satisfactory when the on and orf periods of the impulses supplied'thereto are substantially equal, I provide the second code following relay MR2 and reactance unit RC for controlling the impulses supplied to unit DU. With relay MRI released closing back contact 28 relay MR2 is energized and picked up causing winding 25 of unit RC to be energized and magnetic energy stored in the reactance unitkRC. When relay MRI is picked up forl ar brief period infresponse to ionization of tube VT2 because of a current impulse flowing in thetrack rails, the circuits to the top winding 26 of relay MR2 and to the winding 25 of reactance `unit RC are both opened. The decay of the magnetic energy stored in reactance unit RC causes current to flow in the lower winding 27 of relay MR2. winding 21 is such that the flux set up in relayI MR2 by the current fiowing in winding 21 due to the decay of magnetic energy in unit RCopposes the flux set up by the current iiowing in winding 26 of the relay so that relay MR2 is quickly released. When relay MRI is shortly released in response to the deionization of tube The connection of y f VT2 the top winding 26 of relay MR2 is reenergized but the building up of vflux in relay MR2 by current owing in winding 26 is at first opposed by the flux created by the current iiowing in Winding 2l. The current supplied to winding 27 gradually falls to zero due to the dying away of the energy stored in the reactance device RC so that after a brief period the flux created by winding 2S prevails and relay MR2 is again picked up. The parts are so proportioned that the delay thus @fleet-ed in the picking up of relay MR2 provides substantially equal on and oir periods in the operation of relay MR2 with the result that they current impulses supplied to the coded unit DU over front contact 3B of relay MR2 have substantially equal on and 01T periods. This operation of relay MR2 with respect to the operation ci relay MRI is illustrated by Fig. 5b. It should be noted that when relay MRI is operated at the lower code rate of 120 and '75 cycles per minute the magnetic energy stored in the reactance unit RC is within limits built up to a higher level than at the higher code rate of 180 cycles per minute and as a consequence the energization of winding 2l effected during the decay of the stored magnetic energy in unit RC is able to hold relay MR2 released a longer time at the lower code rates so that substantially equal on and off periods in the operation of relay MR2 occur at each of the code rates of 180, 120 and 75 cycles per minute.

From the foregoing description of the operation of the apparatus of Fig. 1, it is clear that relay TA is picked up and a clear signal is displayed by the cab signal CS in response to current impulses of the code rate of 180 cycles per minute flowing in rails la and Ib and which code rate is used to reect clear traffic conditions, Relay TR is picked up and an approach medium signal is displayed by the signal CS in response to current impulses of 120 cycles per minute and which code rate is used to reflect approach medium traffic conditions. Relay TL is also picked up in response to current impulses of the code rate of '75 cycles per minute so that an approach signal is displayed by the signal CS. Again, when the ctu'rent impulses supplied to the track rails are shunted by a train in advance and all three relays TA, TR and TL are released a slow speed signal is displayed by the signal CS.

It is to be observed that in the event the energy level of the current impulses supplied to the track rails Ia and Ib is relatively high the first stage amplifying tube VTI may not be needed and the induc'tors I8 and I I may be connected directly with the grid 2| and cathode 20 of tube VT2.

Referring to Fig. 2, the train carried apparatus comprises two receiving channels one effectively influenced by coded alternating ciu'rent of 100 cycles per second, such as, for example, disclosed in United States Letters Patent No. 1,773,472, granted August 19, 1930 to P. N Bossart, for Railway traffic controlling apparatus, such coded alternating current being widely used in present day cab signal systems for railways, and the other channel is effectively influenced by low frequency alternating currents such as supplied by the trackway apparatus of Fig. 3 to be described later, the low frequencies being of the order of the code rates of the standard coded alternating current. That is, when the code rates of the standard alternating current of 100 cycles per second are that of 180, 120 and 'l5 cycles per minute or 3, 2 and 11/4 cycles per second, the second channel is effectively influenced by low frequency alternating currents of the frequencies of 3, 2, and 11/4 cycles per second.

Looking at Fig. 2, the train carried inductors IIl and I I mounted in inductive relation with the track rails Ia and Ib, are interposed in the grid circuit of the amplifying tube VTI the same as in Fig. 1, except a low pass filter LPF is included in this grid circuit. The specific form of the low pass filter LPF is immaterial and as here shown it consists of two inductors 46 and 4l and a condenser 48. The parts of the filter LPF are so proportioned that it has a cut off frequency of the order of 3 cycles per second. Hence alternating current of 100 cycles per second is not passed to the tube VTI but alternating currents of the low frequencies of 3, 2 and 11/4 cycles per second are passed to the tube VTI with little attenuation. The other receiving channel which is responsive to coded alternating current of*4 100 cycles per' second includes an electron tube VT3 and a band pass filter BPF. The tube VT3 is preferably a. high vacuum amplifying tube similar to tube VTI. The band pass lter BPF comprises condensers 49 and 5U and a transformer TI. The condenser 49 and primary winding 5I of transformer TI are serially connected across the inductors IG and II in multiple with the grid circuit of tube VTI. The condenser 50 is connected across the secondary winding 52 of transformer TI and the two in multiple are connected across the grid 53 and cathode 54 of tube VT3, to form a grid circuit for that tube, the cathode 54 of tube VT3 being connected to a mid terminal of rcsistor i6 to provide a desired grid bias potential for the tube VT3. Tube VT3 is preferably biased for substantially normal zero plate current. The parts of lter BPF are tuned sharply to resonance at 100 cycles per second. Hence, electromotive forces induced in inductors IB and Il in response to coded alternating current of 100 cycles per second are applied across the grid and cathode of tube VTS but are blocked by filter LPF from tube VTI, whereas electrornotive forces induced in the inductors II) and I I by alternating currents of the low frequencies of 3, 2 and 1% cycles per second are applied to the tube VTI but are blocked from the tube V'T3.

The plate circuit for tube VT3 extends from terminal 32B, over resistor RI, plate 55 of tube VT3, tube space, cathode 54, a portion of resistor I6 and to terminal 32N. The grid circuit of detector tube VT2 of Fig, 2 is coupled with the plate circuit of tube VTI through condensers C2 and resistor R2 the same as in Fig. 1, and consequently it is also coupled with the plate circuit of tube VT3 through the same elements because of the parallel arrangement of the plate circuits of the two tubes VTI and VTS. The Winding 22 of the code following relay MRI is included in the anode circuit of tube VT2, and the deionizing unit consisting of condenser CI and resistor R3 is associated with tube VT2 in the same manner as in Fig. 1.

In Fig. 2, the input side of the decoding unit DU is controlled over a front contact 56 of code following relay MRI. The relays TA, TR and TL connected with the output side of decoding unit DR are responsive to the code rates of 180, 120 and 75 cycles per minute or 3, 2 and 1% cycles per second the same as described in Fig. 1, and the relays TA, TR and TL govern the operating circuits of cab signal CS the same as in Fig. l.

In Fig. 3 there is shown trackway apparatus for supplying to the rails of a track section alternating currents of the low frequencies of 3, 2 and 11/4 cycles per second. Looking at Fig. 3, the track rails Ia and Ib of a section of railway over which traffic normally moves in the direction indicated by an arrow are formed into consecutive track sections by the usual insulated rail joints, and of which track sections only the one section W-X and the ends of the two sections adjacent thereto are shown for the sake of simplicity. Each track section is provided with a track circuit consisting of means for creating different low frequency alternating currents, the track rails and a track relay. Referring to section W-X, the means for creating low frequency alternating currents includes a suitable source of direct current whose terminals are indicated at E and C, three code transmitters ICT, 2CT and 30T, and a reactance device 65 together with the necessary circuit connections with the track rails. The track relay for vsection W-X is a polar code following relay. WHT Whose winding 11 is connected across the rails of section VKL-X, and Whose polar contact member 51 is biased to remain at the position to which it was last operated when the relay is deenergized. When the relay WTR: energized alternately by current; of positive and negative polarity so as to operate its contact member 51, direct current is alternately supplied to the two half portions o the primary winding 58 of a transformer TW so that electromotive forces of a frequency corresponding tc the rate at which the relay WTR is operated are inducedr in the secondary winding 59 of transformer TW. secondary winding 59 is connected with decoding circuits, a rst one of which includes a condenser GD and an inductor 6l and which circuit is tuned to resonance at the .frequency correspondingv to that of the electromotive force produced in. the secondary winding 59 when the relay WTR operated at the rate of 3 cycles per second. A relay WA is connected through a recti r 62. across a portion of the inductor El of tb l decoding circuit and hence relay WA is effectively energized and picked up only when reiay WTR is being operated at the code rate of 3 cycles per second. A seco-nd decoding circuit includes condenser B3 and an inductor 54 and this decoding circuit is tuned to resonance at a frequency corresponding to that of the electromotive force produced in the .secondary winding 59 when relay W'I'R is opera-ted at 2 cycles per second. A. relay WR is connected portion of inductcr 64 through a rcctier 55 and relay WR is effectively energized and picked up only when relay WTR.- is being operated at the code rate of 2 cycles per second. A third decoding circuit including an inductor 66 connected with the secondary winding 59 of transformer TW and this third circuit is non-tuned so that current is passedv through a rectifier 61 to a relay WL when relay XKTRis operated at either the code rate of 3 or cycles per second, and also when relay WTR is operated at thc third code rate of ll/:t cycles por second. The relays WA, WR and WL are used to control the supply of current to the circuit not shown for the section next in the rear of section WL-X, and. also to govern the operating circuits of a wayside signal WS for section Ff-X. The control effected by the relays WA, WR and Wl.. will be shortly explained.

The three relays XA, XR and XL shown at the right-hand end of' Fig. 3 are associated with the track circuit for the section next in advance of section W-X in substantially the same manner that the respective relays WA, WR and WL are associated with the track circuit for the section W--X. That is to say. the relays XA, XR and XL are controlled by the code following track i relay for section next advance of section W-X through decoding circuits so that relays XA and XL are effectively energized and picked up when the code following track rela-y XTR is operated at the code rate of 3 cycles per Y second, relays XR, and XL are effectively energized and picked up when relay XTR, is operated at the code rate of 2 cycles per second, and relay XL is effectively energized and picked up when relay XTR is also operated at the code rate of `t1/4 cycles per second.

The relays XA, XR and XL are used for governing the supply of current to the track circuit for the section W-X and to govern vthe operating circ 3 for the XS for the section next in advance. The operating circuits for l ters and a reactance device together with the necessary circuit connections. The code transmitters ICT, 20T and. BCT are each preferably or" the well known oscillating relay type and each is provided with pole changing contact members which are normally biased to a center position. The code transmitter 3CT is adjusted so that when its winding S8 is supplied with direct current the pole changing contact members 15 and 16 are operated between right-hand and lefthand positions at the rate of 3 cycles per second. The code transmitter ZCT is adjusted so that When its winding' 69 is energized its pole changing contact members 13 and 1S are operated at the rate of 2 cycles per second, and code transmitter ICT is adjusted so that when its winding is energized. its pole changing contact members 80 and 8! operated at the rate oi 11A cycles per second.

Vlhen clear traflic conditions exist in advance of section W--X and the' relay XA is picked up closing front contacts 1| and 12, or when approach medium traflic conditions exist in advance and relay XR is picked up closing front contacts 73 and 14, the winding 68 of code transmitter T is connected across the terminals B and C of the source of direct current over a circuit easily traced so that the code transmitter SCT is energized to operate its contact members 15 and16 at the code rate of 3 cycles per second. Each time the contact members 15 and 16 are closed to the right as viewed in Fig. 3, current of positive polarity is supplied to the track circuit of section W-X, the circuit being traced from terminal B over either front contact 1l or 13, contact member 15 toward the right, Wire 82, track lead wire 83, track rail la, Winding 11 of track relay WTR or train shunt if 'section W--X is occupied, rail Ib, track lead wire 84, winding of reactance device 85, adjustable resistor 86, wire 81contact member 16 toward the right, front contact 12 or 14 and to terminal C of the current source. Each time the contact members 15 and 16 are closed toward the left current of negative polarity is supplied to the track circuit, the circuit being made up of the same elements as traced above except it is now closed at the left-hand contacts of the pole changing contact members 15 and `1li. Consequently for each operating cycle of code transmitter SCT the track circuit of section W-X is supplied with current the polarity of which is positive during substantially the rst half of the cycle and is negative during substantially the second half of the cycle. This condition is illustrated by the flat top curve of Fig. 6. The resistor 86 is interposed in the connection to the 6 nusodal curve of Fig. 6. It is to be observed that if the section W--X is relatively long the impedance of the track rails Ia and Ib may be sufficient to effect a substantially sinusoidal wave form of the current and the unit may not be needed. A resistor 88 may be connected across the track lead wires 83 and 84 to reduce sparking at the contacts of the pole changing contact members 15 and 15. It follows, therefore, that when eit-her clear traiiic conditions or approach mediiun traic conditions exist in advance of section W-X, a track circuit current which in effect is an alternating current of the code irequency of 3 cycles per second is supplied to the track circuit for section W-X and by proper proportioning o parts the wave form of the current is substantially free from distortion.

When. approach traflic conditions exist in advance of section W-X and relays XA and XR are released and relay XL is picked up so that back contacts 88 and 90 of relay XA, back contacts 9| and 52 of relay XR and front contacts 53 and 94 of relay XL are all closed, the winding 69 of code transmitter 2CT is energized and that code transmitter operates its pole changing contact members 18 and 19. Each time contact members 18 and 1B are closed toward the right, current of positive polarity is supplied to the track circuit of section W-X, the circuit comprising terminal B, front contact 93, back contacts 8| and 89, contact member 18 toward the right, Wires 82 and 83, rail la, winding 11 of relay WTR or train shunt ii the section is occupied, rail lb, Wire 84, winding of reactance device 85, resistor 88, wire 81, contact member '79 toward the right, back contacts 853. and 82, iront contact 94 and terminal C. Each time contact members 18 and 19 are closed to the left current of negative' polarity is supplied to the track circuit over this same circuit since the circuit is pole changed by the contact members 18 and 19. Since code transmitter 2CT operates at 2 cycles per second the current of the track circuit of section W-X is effectively an alternating current having a frequency of 2 cycles per second, the Wave form of the track circuit current being substantially that shown by the sinusoidal curve in Fig. 6. It follows that under approach traic conditions in advance of section W-X, alternating current of the low frequency of 2 cycles per second is supplied to the track circuit for section W--X to rellect approach medium traffic conditions for that section.

When the section next in advance of section W-X is occupied so that relay XL is released closing back contacts 95 and S6, the winding 10 of code transmitter ICT is energized and opcrates the contact members 80 and 8| at the rate of 11/4 cycles per second. Each time the contact members 80 and 8| are closed toward the right current of positive polarity is supplied to the track circuit for section W-X, the circuit involving the elementsv` terminal B, back contact 95. contact member 80 toward the right. wires 91 and 83, rail Ict, winding 11 or train shunt, rail Ib, wire 84, winding of reactance device 85, resistor 88, wire S8, contact member 8| toward the right, back contact 86 and terminal C. Each time contact members 80 and 8| are closed toward the left current of negative polarity is supplied to the track circuit of section` W-X over the circuit traced above except as to the position of the pole changing contact members 88 and 8|. Thus, when the track section next in advance oi section W-X is occupied the track circuit Ior section W-X is supplied with current which in eiect is an alternating current of the low frequency of 11/4 cycles per second to reflect approach traflic conditions for that section. Alternating current is supplied to the track circuit for the section next in the rear of section W-X in substantially the same manner as just described for supplying alternating current to the track circuit of section W--X, the alternating current supplied to the circuit for the section next in the rear being controlled by relays WA, WR and WL.

Ii a train equipped with the apparatus of Fig. 2 occupies track section W-X of Fig. 3 under clear traic conditions and alternating current of the low frequency of 3 cycles per second is supplied to the track circuit of that section in a manner explained hereinbefore, the electrometive forces induced in the inductors lll and II add their effects and the resultant electromotive force is applied through the low pass lter LPF to the grid of tube VTI but such electromotive iorce is blocked by the band pass filter BPF from the tube VTS. After amplification of such induced electromotive force by the tube VTI it is applied to the grid of tube VT2 through the coupling condenser C2. The wave form of this induced electromotive force is similar to that of the track circuit current, that is, the induced electromotive force has a sinusoidal Wave form substantially the same as that of the track circuit current which is illustrated by the sinusoidal curve of Fig. 6. During one half cycle of each cycle of the wave form of the induced electrcmotive force the grid 2| oi positive in potential with respect to cathode 2|! so that the tube VT2 is ionized and made conductive, with the result that the code following relay MRI is energized and picked up by the current passed by the tube VT2. With relay MRI picked up closing front contact 24 the condenser CI is connected directly across anode I9 and cathode 20 and the current which was flowing through the tube is momentarily diverted to the condenser, with the result that tube VT2 deionizes and restores to its non-conducting condition. When condenser C| is fully charged current ceases to iiow with the result that the code iollowing relay MRI is released, closing back contact 23 and connecting resistor R3 across the condenser CI. Condenser CI now discharges through resistor R3 and is prepared for being charged when the tube VTZ is next ionized, which will be during the corresponding half cycle of the next cycle of the induced electromotive force. It is clear therefore that during one half cycle of each cycle oi the track circuit current the tube VT2 is ionized so that relay MRI is energized and picked up, and during the interval of the other half cycle of each cycle of the track circuit current the tube VTZ is deionized and restored to its non-conductive condition and relay MRI is deenergized and released, relay MRI being operated therefore at a rate corresponding to the frequency oi the track circuit current. While the other half cycle of each cycle of the induced electromotive force is not used by the train carried apparatus both half cycles of the track circuit current are used to operate the code following track relay of Fig. 3 in the manner explained hereinbefore.

With code following relay MR| operated at the code rate of 3 cycles per second current impulses at the rate of 3 impulses per second are supplied to the input side ol the decoding unit DU over tube VT2 is driven more front contact 56 of relay MRI with the result that relays TA and TL connected with the output side of the unit DU are energized and picked up. When relay TA of Fig. 2 is energized and picked up a clear indication is displayed by signal CS.

If approach medium traffic conditions exist for section W-X and alternating current of 2 cycles per second is supplied to the track circuit of the section the operation of the train carried apparatus of Fig. 2 is similar to that described under clear trafic conditions except for the fact that the relay MRI is now operated at the rate of 2 cycles per second. Current impulses at the rate of 2 impulses per second are now supplied to the decoding unit DU and relays TR and TL are picked up with the result that signal CS displays an approach` medium indication. Again under approach traiiic conditions and alternating current of 11/4 cycles per second is supplied to the track circuit of section W-X, the operation of the train carried apparatus of Fig. 2 is similar to that described above except for the fact that relay MRI is now operated at the code rate of 1.1/5l cycles per second. This time current impulses as the rate of 1% impulses per second are supplied to the decoding unit DU and relay TL only is picked up causing signal CS to display an approach indication. With section W-X already occupied by a train when the train on which the apparatus of Fig. 2 is mounted enters the track section the leading train shunts the track circuit current so that the code following relay MRI is inactive and all of the relays TA, TR and TL are released, with the result that signal CS displays a slow speed signal.

In the event the train equipped with the apparatus of Fig. 2 is moving through a stretch of railway provided with track circuits using alternating current of cycles per second` coded at the standard code rates of 180, and 75 cycles per minute or 3, 2 and 1.1/4 cycles per second such as disclosed in the aforementioned Bossairt Patent No. 1,773,472, the clectromotive force induced in inductors IIJ and I I during each on period of the coded alternating current of 100 cyclesk per second will be an alternating electromotive force of 100 cycles per second and will be passed by the band pass lter BPF to the tube VT3 with the result that current will flow in the plate circuit of that tube during each on" period of the track circuit current and the plate current will cease during each "ol period of the track circuit current because tube VT3 is biased for substantially normal zero plate current. 'I'he change in the voltage drop across resistor RI thus effected by the plate circuit current of the tube VT3 causes an electromotive force to be applied to the grid 2l of tube VT2 which periodically drives the grid 2l more positive in potential with respect to cathode 20 at a rate corresponding to the code rate of the alternating current. Each time grid 2| is driven more positive in potential the tube VT2 ionizes and becomes conductive so that relay MRI is energized and picked up. Tube VT2 is deionized and rendered non-conductive through the medium of condensers CI subsequent to each period of ionization, with the result that relay MRI is operated at a rate corresponding to the code rate of the alternating track circuit current. With relay MRI thus operated the signal CS is made to display an indication corresponding to the code rate of the coded alternating track circuit current through the medium of the decoding It follows from the foregoing description that n the train carried apparatus of Fig. 2 is operated by either the standard coded alternating current l of 100 cycles per second as supplied to a track circuit by the trackway apparatus of the aforementioned Bossart Patent No. 1,773,472, or by alternating current of the low code frequency of 2 and 11/4 cycles per second as supplied to a track circuit by the trackway apparatus of Fig. 3 and which low frequencies correspond to the code rate of the standard 100 cycle alternating current.

In the event more equal on and olf periods for the impulses supplied to the decoding unit DU o1 Fig. 2 is desired, the second code following relay MR2 and reactor R3 of Fig. 1 maybe added to the apparatus of Fig. 2, relay MR2 and reactor R3 being governed over back contacts of relay Y MRI and the impulses supplied to the decoding unit DU being governed over a front contact of relay MR2, the same as shown in Fig. l.

It should be noted that with the train carried apparatus oi' Fig. 2 the tube VT2 need not be of the controlled ionization type, and a high vacuum low plate voltage tube can be used. In this latter case the tube VT2 would ber normally biased to the straight line portion of the grid voltage plate current characteristic and relay MRI would be governed through the medium of a transformer, the primary winding of which transformer would be interposed in the plate circuit of the tube and the secondary winding of the transformer would be connected with the winding 22 of relay MRI.

In Fig. 4 the train carried apparatus is provided with two receiving channelsthe same as in Fig. 2. In Fig. 4, however, the amplifying tube VTI functions to amplify both the standard coded alternating current of 100 cycles per second and to amplify the low frequency alternating current. The low pass filter LPF of Fig.4 consists of two inductors 9S and IOO and two condensers IUI and |02. The band pass filter BPF is the same as in Fig. 2. The primary winding 5I and condenser 49 or" band pass lter BPF are serially connected across inductors I0 and II. Inductors Ill and i I are also connected with the grid IT and cathode I5 of tube VTI through the low passy filter LPF, the secondary winding 52 of transformer T2 of the band pass filter BPF, and a control unit consisting of a condenser C6 and a resistor R6 in multiple. The plate circuit of tube VTI is coupled with the grid circuit of tube VT2 the same as in Fig. 2. Also, in Fig. 4, the code following relay MRI, the deionizing unit consisting of condenser CI and resistor R3. decoding unit DU, relays TA, TR and TL, and the cab signal CSare associated with the tube VT2 in the same manner as in Fig. 2.

When energy is received by inductors Ill and II of Fig. 4 in response to coded alternating current of 100 cycles per second flowing in rails Ia and lb as would be the case of a track circuit of theaforementioned Bossart Patent No. 1,773,472,

such energy is blocked by the low pass lters LPF but is effective to induce an electrornotive force in the secondary winding 52 of transformer TI of the band pass filter BPF'. The electromotive force thus induced in the secondary winding 52 is applied to the grid I l of tube VTI over a circuit which can be traced from the right-hand terminal of secondary winding 52, through condenser C' and resistor R6 in multiple, grid Il, tube space to cathode I5, lower portion oi reing variation in the plate circuit ccrrent oi tube VTi. The change in the voltage drop across resistor Rl eiected by this change in the plate circuit current oi tube VTi causes a corresponding change in the potential of grid 2l with respect "-'r to cathode 20 of the tube VTZ so that tube VTZ is ionized periodically at a rate corresponding to the code rate oi the alternating current flowing in the rails la and lb. The tube VTi is deionized subsequent to each period of ionization through the medium of condenser Cl in the manner already explained, with the result that the code following relay MR! of Fig. 4 is operated at a rate corresponding to the code rate of the coded alternating current of 100 cycles. With code following relay MR! thus operated impulses of current are periodically supplied over iront contact E5 of relay MRl to the decoding unit DU at a rate corresponding to the code rate of the track circuit current and the cab signal CS is made to display an indication corresponding to the code rate in the manner explained hereinbefore.

When energy is received by inductors I0 and l! of Fig. 4 due to a low frequency alternating current such as effected by the track circuit apparatus of 1ig. 3, the energy is passed by the lovv pass filter LPF and applied to the grid of tube VTI, the secondary winding 52 oi transformer Tl and condenser C6 offering but little attennation to the energy.

From this point on the operation of the apparatus oi Fig. 4 in response to low frequency alternating current flowing in the track circuit is the same as that described for the apparatus of Fig. 2 and the description need not be repeated.

It follows that the apparatus of Fig. #i is responsive either to coded alternating current of 100 cycles per second such as provided by the trackivay apparatus of the aforementioned Bossart Patent No. 1,773,472, or to alternating current of low code frequencies such as provided by the trackway apparatus of Fig. 3.

Although I have herein shown and described only certain forms of apparatus embodying my invention. it is understood that various changes and modications may bc made ther-in Within the scope ol the appended claims Without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

l. In a signal system for a railway having its rails formed with a track section which is provided Witn trackway apparatus having successive operation cycles each of a predetermined interval and operative at times to supply to the rails of that section during each cycle a single effective current impulse the duration of which impulse is short and only a small portion of the operation cycle interval, the combination comprising, a train carried normally deenergized rst code iollowing relay, train carried receiving and amplifying means mounted on the train in inductive relation with the track rails and connected with a winding of said relay for energizing the relay during each such current impulse supplied to the rails whereby said relay is operated with unequal on and off periods, a second code following relay having a rst and a second winding which are connected to produce opposing magnetic iiuxes in that relay, a reactance device including a Winding mounted on a magnetic core, a rst energizing circuit for said second relay including a back contact of said rst relay and said iii-st winding of said second relay, another circuit including a back contact of said rst relay and a front contact of said second relay and the winding of said device for storing magnetic energy in said device, a second energizing circuit of said second relay including a portion of the Winding of said reactance device and said second Winding of said second relay whereby said second relay is provided With slow pickup characteristic and is operated in response to the current impulses supplied to the track rails with substantially equal on and ofi periods, and signaling means controlled over a contact of said second relay.

2. In a Signal system for railways having transmitting apparatus which is eiective to divide time into successive operation cycles each of a predetermined interval and to supply diuing each cycle a single signaling current impulse the duration oi which impulse is short and only a small portion of the operation cycle interval, the combination comprising, receiving circuit means for receiving energy from such transmitting apparatus, a rst code following relay connected with said receiving circuit means effectively energized and picked up during the short interval of each said current impulse, a second code following relay having a. iirst and a second winding connected to create opposing magnetic iiuxes, a reactance device having a Winding with a magnetic core, a rst energizing circuit for said second relay including a back contact of said rst relay and said rst Winding; another circuit including a back contact of said first relay, a front contact o! said second relay and the Winding of said device for storing magnetic energy in said device; a second energizing circuit for said second relay including a portion of the winding of said device and said second relay for delaying the picking up of said second relay for operating said second relay once each operation cycle of the transmitting apparatus with substantially equal on and off periods, and a signaling circuit controlled over a contact of said second relay.

3. Train carried signa-ling apparatus for use with either a rst territory provided with track circuits supplied at times with alternating current of a given frequency coded at a predetermined rate or with a second territory provided with track circuits supplied at times with alternating,r current of a frequency equal to said predetermined code rate comprising, a receiver mounted on the train for receiving energy from such track circuits, a controlled ionization tube. a code following relay, a source of direct current, a reactance device, said relay and source of direct current connected across the anode and cathode of said tube to energize said relay when an impulse of electromotive force of positive polarity is applied to the grid of said tube causing the tube to ionize, said reactance device connected with the anode and cathode of the tube to deionize the tube subsequent to each such impulse of electromotive force, tivo parallel circuit channels ior coupling said receiver with said grid and cathode, a selected one oi said channels including a band pass `lter tuned to resonance at said given frequency and operative to apply to said grid an impulse of electromotive force of positive polarity in response to each on period of said coded alternating current of said given frequency for operating said code following relay at said code rate when the train traverses a track circuit of said first territory, the other of said circuit channels including a low pass lter tuned for a cut-ofi frequency equal to said code rate and operative to apply to said grid an` impulse of electromotive force of positive polarity in response to each cycle of said alternating current of a frequency equal to said code rate for operatingr said code following relay at said code rate when the train traverses a track circuit of said second territory, and a signaling circuit including a contact of said code following relayeffectively controlled when said relay is operated at said code rate.

4. Train carried signaling apparatus for use with either a first territory provided with track circuits supplied at times with yalternating current of a given frequency coded at a predetermined rate or with a second territory provided with track circuits supplied at times with alternating current of a frequency equal to said predetermined code rate comprising, a receiver mounted on the train for receiving energy from such track circuits, an velectron tube detector, a code following relay connected with the output terminals of said detector, said relay normally deenergized and effectively energized when positive energy is applied to the input `terminals of said detector, two parallel circuitv channels for coupling said receiver with the input terminals of saiddetector, a selected one of said circuit channels including a band pass filter tuned to resonance at said given frequency and voperative to apply to the inputfterminals of said detector an impulse of positive energy in response to each on period of said coded alternating current of said given frequency for operating said code following relay at said code rate vwhen the train traverses a track circuit of said first territory, the other of said circuit channels including a low pass filter having a cut-oil frequency equal to said predetermined code rate and operative to' apply to the input terminals of said detector an impulse of positive energy in response to each cycle of said' alternating current of a frequency equal to said code rate for operating said code following relay at said code rate when the train traverses a track circuit of said second territory, and signaling means including a contact of said relay effectively energized when the relay is operated at said code rate.

5. Train carried signaling apparatus for use with either a first territory provided with track circuits supplied at times with alternating current of a given frequency coded' at a predetermined rate or with a second territory provided with track circuits supplied at times with alternating current of a frequency equal to said predetermined code rate comprising, a receiver mounted on the train for receiving energy from such track circuits, a controlled ionization tube, a code following relay, a source of direct current, a reactance device, said relay and source of direct current connected across the anode and cathode of said tube to energize said relay when an impulse of electromotive force of positive polarity is applied to the grid of said tube causing the tube to ionize, said reactance device connected with the anode and cathode of the tube to deionize the tube subsequent to each such impulse of electromotive force, a rst and a second amplifier tube, a resistor common to the plate circuits of said amplifier tubes and coupled with the grid of said controlled ionization tube to apply an impulse of electromotive force of posi- `r tive polarity to the grid of the last mentioned tube when a predetermined voltage change is effected across said resistor, a first circuit channel including a band pass filter tuned to resonance at said given frequency to connect said receiver with the grid of said first tube to effect 'said voltage change across said resistor'in response to eachon period of said coded alternating current for operating said code following relay at said code rate when the train occupies a track circuit of said first territory, a second circuit channel including a low pass lter tuned with a cut-off frequency equal to said code rate to connect said receiver with the grid of said second amplifier tube to effect said voltage change acro said resistor in response to each cycle of said alternating current of a frequency equal to said code rate for operating said code following relay at said code rate when the train occupies a track circuit of said second territory, and signailing means including a contact of said relay effectively energized when the relay is operated at said code rate. f

6. Train carried signaling apparatus -for use with either a first territory provided with track circuits suppliedv at times with alternating current of a given frequency coded at a predetermined rate or with a second territory provided with track circuits supplied at times with alternating current of a frequency equal to said predetermined code rate comprising, a receiver mounted on the train .for receiving energy from such track circuits, a controlled ionization tube, a code following relay, a source of direct current, a reactance device, said relay and source of direct current connected across the anode and cathode of said tube to energize said relay when an impulse of electromotive force of positive polarity is applied to thegrid of said tube causing `the tube to ionize, said reactance device connected withk the anode and cathode of the tube y to deionize the tube subsequent to'each such impulse of electromotive force,v an amplifier tube, a plate circuit for said. amplifier tube coupled with the grid of said controlled ionization tube to apply an impulse of electromotive force of positive polarity t-o the grid ofthe last mentioned tube when a predetermined change of the plate circuit current ofthe amplifier `tube is effected, a first circuit channel including a band pass filter tuned to resonance at said given frequency and a blocking condensei` to connect said receiver with the grid of said amplifier tube to effect said cha-nge in its plate circuit current in response to each on period of said alternating current of said given frequency to operate said code following relay at said code rate when the train occupies a track circuit of said first territory, a second circuit channel including a low pass filter tuned for a cut-off frequency equal to said code rate to connect said receiver with the grid of said amplifier tubeto effect said change in its plate circuit current in response Ato each cycle of said alternating current of a frequency equal to said code rate to operate said code following relay at said code rate when the train occupies a track circuit of said second territory, and signaling means including a contact of said relay effectively energized when the relay is operated at said code rate.

7. Receiving apparatus for use with a source fil,

of periodic impulses of current which are of short duration as compared with the duration between successive impulses comprising, a controlled ionization tube having a grid coupled with said source of current impulses to effect ionization of the tube by each such impulse, a first code following relay and a source of direct current connected across the anode and cathode of said tube to energize said relay when the tube is made conductive, a condenser connected with said anode and cathode to deionize the tube subsequent to each said impulse of current, a second code following relay, an energizing circuit including a back contact of said iirst relay and a winding of said second relay to pick up said second relay when said rst relay is released, means including a back contact of said first relay to effect a predetermined slow pick-up period for said second relay to cause said second relay to be Operated at substantially equal on and off periods in response to said current impulses, and a signaling circuit including a contact of said second relay.

8. Receiving apparatus for use with a source of periodic impulses of current of different code rates and which current impulses are of short duration as compared with the duration between successive impulses comprising, a controlled ionization tube having a grid coupled with said source of current impulses to cause ionization of the tube by each such impulse, a first code following relay and a source of direct current connected across the anode and cathode of the tube to energize the relay when said tube is ionized, a condenser connected with said anode and cathode to deionize said tube subsequent to each such impulse whereby said rst relay is operated at the code rate of the current impulse but with unequal on and oir periods, a second code following relay having a iirst and a second winding, an energizing circuit including a back contact of said rst relay and said iirst winding oi said second relay to pick up the second relay when said first relay is released, a reactance unit including a winding a portion of which is connected with the second winding of said second relay, another circuit including a back contact of said rst relay and said winding of said reactance unit to store energy in said unit to cause current to flow in the second winding of said second relay that modifies the energization of the second relay as effected by said energizing circuit to cause said second relay to be operated at the code rate of said current impulses with substantially equal on and off periods, and decoding means selectively responsive to said different code rates controlled over a front contact of said second relay.

9. Receiving apparatus for use with a source of periodic impulses of electromotive force connected with the grid of a controlled ionization tube for causing ionization of the tube by each such impulse of electromotive force comprising, a code following relay and a source cf direct current connected in series across the anode and cathode of said tube to pick up said relay when the tube is ionized and made conductive, a condenser, circuit means including a front contact of said relay to connect one terminal of said condenser directly with the anode of the tube and the other terminal of the condenser directly with the cathode of the tube to divert the current flowing through said relay to said condenser when the relay is picked up to deionize the tube and to retain the relay picked up until the condenser is fully charged, a resistor, means including a back contact of said relay to connect said resistor across said condenser to discharge the condenser between successive impulses of said electromotive force, and signaling means including a contact of said code following relay effectively controlled when the relay is operated.

10. Receiving apparatus for use with a source of periodic impulses of electromotive force connected with the grid of a controlled ionization tube for causing ionization of the tube by each such impulse of electromotive force comprising, a code following relay and a source of direct current connected in series across the anode and cathode of said tube to pick up said relay when the tube is ionized and made conductive, a condenser, circuit means including a front contact of said relay to connect said condenser and said relay in series across said source of direct current to divert the current flowing in said relay to said condenser to deionize said tube when the relay is picked up and to retain said relay picked up until said condenser is fully charged, a resistor, means including a back contact of said relay to connect said resistor across said condenser to discharge the condenser between successive impulses of said electromotive force, and a signaling circuit including a front contact of said relay eiectively energized when said relay is operated.

WILLARD P. PLACE. 

